Unknown: Hodgkin Disease
Unknown: Hodgkin Disease
Hodgkin disease, also known as Hodgkin lymphoma or HL, is a cancer of the blood and lymphatic system. It is the most common type of blood cancer and the third most common childhood cancer. The disease is named for Thomas Hodgkin (1798–1866), the British doctor who first described it in 1832.
Hodgkin disease is one of the two major types of lymphoma, a form of cancer that originates in lymphocytes, which are a specific type of white blood cells in the immune system. It is unusual in that it primarily affects two different age groups, adolescents and young adults between the ages of fifteen and thirty-five, and older adults over age fifty-five. Hodgkin begins in the lymphatic system, a group of organs and tissues that are part of the immune system and also help to form new blood cells. The lymphatic system includes lymph nodes, small organs composed of
lymphoid tissue located at various points throughout the body that are joined by lymphatic vessels; the spleen, a small organ on the left side of the abdomen; the bone marrow; and the thymus gland, which is just below the neck.
Hodgkin disease begins when a type of lymphocyte called a B cell turns into an abnormal form called a Reed-Sternberg cell. These abnormal cells continue to reproduce themselves until they form a tumor. In most cases this first tumor develops in one of the lymph nodes above the diaphragm (the thin sheet of muscle that divides the chest cavity from the abdominal cavity); however, the tumor can develop in a group of lymph nodes or elsewhere in the lymphatic system. The disease usually spreads from lymph node to lymph node along the lymphatic vessels rather than skipping around the body. In the later stages of the disease, it spreads outside the lymphatic system to other organs.
There are two basic subtypes of Hodgkin disease: classic, which accounts for 95 percent of cases, and nodular lymphocyte predominant Hodgkin disease (NLPHD), which accounts for the remaining 5 percent. NLPHD differs from classic Hodgkin diseae in that it occurs primarily in lymph nodes in the neck and armpits, and its large abnormal cells are known as “popcorn” cells because they look like pieces of popped popcorn under the microscope.
Hodgkin lymphoma is a relatively rare form of cancer, affecting two or three people in every 100,000. It accounts for less than 1 percent of cancers worldwide. As of 2008, there were about 500,000 people in the United States with some form of lymphoma, but only 143,000 had Hodgkin disease. According to the National Cancer Institute (NCI), about 8,200 new cases of HL are diagnosed in the United States each year, and 1,350 people die from the disease annually.
The rates for Hodgkin disease vary according to race and sex. The highest rates are in Caucasian males (3.2 cases per 100,000), followed by African American males (3.0 cases per 100,000), Caucasian females (2.6 cases per 100,000), African American females (2.1 cases per 100,000), Asian American males (1.4 cases per 100,000), and Asian American females (1 case per 100,000). About 10 percent of cases of Hodgkin are diagnosed in children below the age of fourteen; 85 percent of these are boys.
Although the cause of Hodgkin disease is still unknown, researchers have identified several factors that increase a person's risk of developing this form of cancer:
- Age between fifteen and thirty-five or over fifty-five
- Male sex
- Infection with Epstein-Barr virus or infectious mononucleosis
- Family history of Hodgkin disease
- HIV infection
- Organ transplantation or other reasons for therapy that suppresses the immune system
Although researchers know that Hodgkin disease begins with the formation and multiplication of abnormal cells, they do not yet know what triggers this formation. Some scientists think that certain types of viral infections, genetic factors, or environmental toxins might be involved.
The symptoms of Hodgkin disease include:
- Swelling of the lymph nodes in the neck, armpits, or groin. These are usually painless.
- Tiredness that does not go away.
- Fever and chills.
- Night sweats.
- Unexplained weight loss of 10 percent or more of body weight.
- Itchy skin.
- Loss of appetite.
Some patients also experience heavy sweating, coughing or chest pain, difficulty breathing, enlargement of the spleen, hair loss, or neck pain.
The doctor usually begins by taking a medical history, because there are many causes other than Hodgkin for swollen lymph nodes, fever, and some of the other early symptoms of the disease. In some cases, a patient with classic Hodgkin has no early symptoms, and the disease is discovered during a routine chest x ray.
In most cases the disease is diagnosed by a tissue biopsy. The doctor removes a small piece of tissue from a swollen lymph node either by cutting directly into the swollen node or by withdrawing a tissue sample through a fine needle. In addition to looking for abnormal cells in the tissue sample, the doctor may use certain types of chemical tests to look for proteins attached to the surface of the abnormal cells.
In addition to a tissue biopsy, the doctor may order blood tests or a bone marrow biopsy. Blood tests are useful in evaluating the type of chemotherapy that would be best for the patient. In addition, imaging tests can be used to determine the location and extent of the disease. These tests may include x-ray studies, magnetic resonance imaging (MRI), computed tomography (CT) scans, positron emission tomography (PET) scans, and a gallium scan. This last type of test uses a radioactive element given intravenously to identify affected lymph nodes.
The first step in treating any kind of cancer is called staging. Staging is a description of the location of the cancer, its size, how far it has penetrated into healthy tissue, and whether it has spread to other parts of the body. Hodgkin disease is classified into four stages:
- Stage I: The disease is limited to one lymph node.
- Stage II. The disease involves two or more lymph nodes on the same side of the diaphragm.
- Stage III. The disease has spread to lymph nodes on both sides of the diaphragm and may involve the spleen.
- Stage IV. The disease has spread to one or more organs outside the lymphatic system, such as the lungs or liver.
The next steps in treatment depend on the stage of the disease.
- Stage I and Stage II Hodgkin disease can be treated with radiation therapy, chemotherapy, or a combination of both. Only low-dose radiation therapy is used in girls and women, because standard doses of radiation will increase their risk of breast cancer in later life.
- Stages III and IV. Chemotherapy may be used by itself to treat advanced-stage Hodgkin as well as being combined with radiation therapy. There are five different combinations of drugs that are currently used; some of these are quite toxic and have severe side effects. The drug combination preferred by most doctors in the United States is called ABVD, the initials of the four drugs that are administered.
Patients who are not cured by radiation therapy and chemotherapy, or whose disease recurs after chemotherapy, may be treated with a combination of high-dose chemotherapy and bone marrow transplantation. The bone marrow transplantation is needed because the high doses of anti-cancer chemicals will damage the patient's own bone marrow and lead to a life-threatening shortage of the red and white blood cells produced in the bone marrow.
Hodgkin disease is potentially curable, although the treatments that are currently used increase the patient's risk of developing a second type of cancer later in life. As of 2008, 90 percent of patients with Stage I or II disease lived for five years after treatment. The five-year survival rates for Stages III and IV are 84 percent and 65 percent respectively. Between 20 and 25 percent of all patients diagnosed with Hodgkin will die of the disease. In the first fifteen years after treatment, recurrent Hodgkin is the major cause of death among patients; after fifteen years, death from other causes is more common.
There is no way to prevent Hodgkin disease, because its causes are still unknown.
Current research on Hodgkin disease is focused on the possible role of viruses in causing the disease and on exploring newer forms of treatment. Although radiation therapy and chemotherapy are highly effective treatments for this form of cancer, they have a number of long-term as well as short-term side effects. Because Hodgkin disease is a relatively rare form of cancer and because there are still unanswered questions about the best way to treat it, researchers are actively looking for Hodgkin patients to participate in clinical studies.
SEE ALSO Infectious mononucleosis; Lymphoma
WORDS TO KNOW
Diaphragm: A sheet of muscle extending across the bottom of the rib cage that separates the chest from the abdomen.
Lymph nodes: Small rounded masses of lymphoid tissue found at various points along the lymphatic vessels.
Lymphocyte: A type of white blood cell that fights infection. Lymphocytes are divided into two types, T cells (produced in the thymus gland) and B cells (produced in the bone marrow).
Popcorn cell: An abnormal cell found in nodular lymphocyte predominant Hodgkin disease (NLPHD).
Reed-Sternberg cell: An abnormal type of B lymphocyte that is found in classic Hodgkin lymphoma.
Staging: Measuring the severity or spread of a cancer.
Thymus: A small organ located behind the breastbone that is part of the lymphatic system and produces T cells.
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